Technical Abstract:
The use of edible films as carriers of antimicrobial plant essential oils and other phytochemicals constitutes an approach for external protection of food systems to reduce surface microbial populations and to enhance oxygen-barrier properties, thus enhancing food safety as well as shelf life. The objective of this study was to investigate the antimicrobial effects of 0.1-0.5% suspensions in apple puree and pectin used to prepare edible films of the following essential oil/oil compounds against the foodborne pathogens Escherichia coli Ol57:H7 and Salmonella enterica: oregano oil/ carvacrol; cinnamon oil/cinnamaldehyde; lemon grass oil/citral, as well as their effect on physical and barrier properties of apple puree-pectin based films. Bactericidal activity of apple puree based film forming solutions was tested against the foodborne pathogen Escherichia coli 0157:H7 and Salmonella enterica in terms of the achievement of a 50% decrease in the initial number of bacteria (BASa). Water vapor permeability (WVP), oxygen permeability (O^P) and tensile properties of apple purec-pectin edible films, with and without plant essential oils and oil compounds, were also compared. BA50 values against E. coli after incubation for 60 min at 21"C ranged from 0.011% for carvacrol to 0.094% for cinnamon oil. The corresponding range against Salmonella was from 0.0052% for carvacrol to 0.041% for cinnamaldehyde. The data also show that (a) the test samples were 2-3 times more effective against Salmonella than against E. coli; (b) the approximate order of antimicrobial activities were as follows: carvacrol > oregano oil > citral > cinnamaldehyde > lemon grass oil> cinnamon oil; and (c) addition of plant essential oils/oil compounds into the apple puree films decreased water vapor permeability, increased oxygen permeability, but did not significantly alter tensile properties. These results show that the plant-derived substances can be used to prepare apple-based antimicrobial edible films or coatings to protect foods against pathogenic microorganisms.